This invention relates to a through-hole pin and connection for laminated circuit elements and a method of connection. More particularly, this invention relates to a new and improved through-hole pin and connection method of using the same, which effects an electrical and mechanical connection between circuit patterns in a laminated circuit element as well as guiding solder material into difficult to reach land areas within the through-hole.
Typically, laminated circuit elements consist of a plurality of individual printed circuit elements, i.e., printed circuit or wiring boards (each consisting of an insulating substrate with circuit traces or pattern thereon), which are laminated together. These multi-layer circuit elements are often used in electronic devices which require high-density wiring. Electrical connections among the various individual circuit elements in such laminated multi-layer circuit elements are usually effected by through-holes that are formed and aligned in each individual circuit element. The vertical through-holes may be formed in each circuit layer prior or subsequent to the layers being laminated. The area on each circuit element surrounding the periphery of each individual through-hole is defined as a land region. Solder is flowed into the through-hole whereby the land regions of each printed circuit element in the laminated circuit are connected to each other.
Unfortunately, many problems and deficencies have been encountered during the above through-hole/solder process. For example, when the solder is flowed into the through-hole, it is difficult to flow the solder smoothly because of its high surface tension. A well known method of facilitating the solder flowing is by using a conductive circular rod. This circular rod, which has a smaller diameter than to the through-hole, will act as a guide while the solder is being poured into the through-hole. However, because the inside circumference of the hole through the land region (i.e. the inside circumference of the opening in the conductive area) is generally withdrawn somewhat from the inside circumferential face of the through-hole in the insulating substrate, it is extremely difficult to bring the circular rod into contact with the recessed land region. As a consequence thereof, the flowing solder does not reach the recessed or withdrawn area of each land region resulting in poor solder flow and poor electrical connections.
Other conventional methods for connecting the land regions of laminated circuit elements, in addition to the aforementioned soldering process, include the well known plating and conductive paste methods. Unfortunately, the plating method is a burdensome and time consuming procedure involving a large number of processes. Similarly, the conductive paste method has problems associated therewith. For example, electrical connections is not reliable, and there is the possibility of peeling in the case of laminated multilayer elements comprised of individual flexible circuit elements.